Trilloch

A trilloch is invisible and nearly impossible to sense. Detect magic cast within 60 feet of its core reveals a pulsing ripple of negative energy that keeps no steady size, color or form.

It cannot attack and cannot be physically harmed. Its essence is a knot 2 to 6 feet wide, but its presence fills a sphere 60 feet across, and it can feed only on deaths inside that zone. Because it eats the ebbing vitality of dying creatures, it must find one or engineer one.

Within the sphere, all attack and damage rolls gain +1 and morale checks +3, so fights tend to run to the end. It also provokes violence: creatures of animal or non-ratable Intelligence within 60 feet begin attacking whatever is close. Brighter beings save vs. spell or spend 1d6 rounds attacking anyone they see as an enemy, or 1d4 rounds attacking whoever is near if no enemy exists, always picking targets within the sphere. The save is rolled only on first exposure, though meeting another trilloch after 24 hours calls for a fresh one. The trilloch relies on brawls continuing after the urge fades.

Since detect magic must be cast from inside its reach, spotting it is risky. Dispel magic chases it off, and an appropriate banishment returns it to its home plane.

Alone by nature, a trilloch often shadows an unknowing host, some powerful beast that kills often, and feeds on its prey. If the host dies, it usually follows the killer. It has only animal wits and no cruelty; suffering gives it nothing, and a painless death nourishes it equally. It is a predator with odd methods, though few can see it as anything but evil.

Unlike other negative-plane natives, it never drains life directly, only taking what escapes the dying. Microbes, normal insects and tiny worms are too small to sustain it, but almost any larger creature, clever or not, will serve.